This study aims to compare a new three-dimensional ultrasound machine with MUGA and MRI in evaluating the heart function of patients with primary pulmonary hypertension. A newly-developed ultrasound volumetric imaging system will be used to acquire the entire volume of the LV chamber approximately 22 times per second. Forty subjects will be enrolled, and will be recruited from patients with primary pulmonary hypertension who are scheduled to undergo MUGA and MRI procedures. The additional three-dimensional uiltrasound and two-dimensional echocardiograpohy will require approximately twenty minutes.